Invisible seam deployment door installation with stabilized air bag deployment opening construction

ABSTRACT

An installation and method is disclosed for mounting an air bag system in an opening in an instrument panel. A stabilizer frame is fixed around the opening in an instrument panel substrate and anchored to a fixed substructure, restraining bulging movement of the instrument panel to rapidly develop shearing stresses in the covering layer by the pressure exerted by the deployment door substrate panel as it is pushed open by the inflating air bag.

BACKGROUND OF THE INVENTION

This invention concerns air bag safety systems for passenger vehiclesand more particularly the formation of a deployment opening which allowsthe air bag to be inflated and to enter the passenger compartment of thevehicle.

In many designs, a deployment opening is formed by a hinged door ordoors fit into an opening formed in the trim structure behind which theair bag is installed. Upon initiation of the air bag system, the air bagis rapidly inflated forcing the deployment door to hinge open and allowthe air bag to deploy into the passenger compartment.

An example of this is shown in U.S. Pat. No. 4,893,833 issued on Jan.16, 1990, for a "Closure for an Air Bag Deployment Opening". In thatdesign, frangible shearing tabs are relied on to secure the deploymentdoor against opening which frangible tabs is sheared off upon theinflation of the air bag exerting pressure on the inside of thedeployment door.

For another example see also U.S. Pat. No. 4,989,896 issued on Jan. 5,1991, for a "Double Door Closure for an Air Bag Deployment Opening".

In such designs the deployment an door is readily visible to the vehicleoccupants. For improved styling and to not invite tampering, there hasbeen developed invisible seam deployment door installation in which thedeployment door and the outline of the opening to be formed are notvisible but rather the area whereat the deployment door will be formedwhen the air bag system is operated is overlain by a smooth covering asof a vinyl covering layer.

In this instance, it is necessary to cut through the covering layer uponinitiation of the air bag system operation.

A decorative covering layer of vinyl is relatively tough and difficultto sever. It is also critical to proper operation that the air bagdeployment occur within a very brief time span, on the order of severalmilliseconds.

Significant delay in the deployment of the air bag can defeat orseriously impair the effectiveness of the air bag system.

In U.S. Pat. No. 5,217,244 issued on Jun. 8, 1993, for an "Arrangementfor Forming and Air Bag Deployment Opening", and U.S. Pat. No. 5,080,393issued on Jan. 14, 1992, for a "Method and Apparatus for Forming an AirBag Deployment Opening" there is described the use of linear energygenerating elements to completely or partially degrade the vinyl in apattern overlying the deployment door or doors such as to ensureinstantaneous severing of the covering layer.

U.S. Pat. No. 5,082,310 issued on Jan. 21, 1992, for an "Arrangement forProviding and Air Bag Deployment Opening" describes an arrangement forpreweakening of the covering layer and exerting an increased pressure bythe deployment doors such as to ensure severing of the covering layer.

For both the single and double door installations, the severing of thecovering layer depends in large measure on the shearing effect createdby the stationary covering layer bonded to the adjacent instrument panelstructure and the moving section of covering layer attached to thedeployment door.

The shearing of the entire perimeter of the single door installation isparticularly critical inasmuch as a single door design requires agreater extent of hinging movement of the deployment door in order toallow the air bag to pass through the deployment opening.

The present inventors have discovered that the adjacent structure of thetrim piece, i.e., the instrument panel defining the opening into whichthe deployment door is fit, may distort appreciably during the air bagdeployment and that this distortion will substantially affect the shearsevering of the covering layer around the perimeter of the deploymentdoor.

A substrate panel defining the deployment door and the adjacentinstrument panel substrate are joined by the overlying covering layerwhich extends over both in the invisible seam design. An intermediatefoam layer is typically included. The foam layer is bonded to both thecovering layer and the deployment door substrate panel and theinstrument panel substrate.

Thus, as the deployment door substrate panel attempts to hinge open, aforce is exerted on the instrument panel structure tending to bulge theinstrument panel structure outwardly.

This outward bulging creates several effects. Firstly, the bulging ofthe instrument panel itself to a significant degree delays thedevelopment of sufficient shear forces to sever the covering layermovement of the instrument panel with the deployment door relieves shearstress and movement.

Secondly, the instrument panel bulging, combined with the bulging of thedeployment door from its center tends to convert the shear stress into atensile stress of the covering layer. The covering layer, usuallyconstructed of a plastic material such as vinyl, is able to elongate toa great extent under tension prior to failure particularly of elevatedambient temperatures.

Accordingly, a stretching tendency results in a substantial furtherdelay in completing the severing of the covering layer.

There also results a mispositioning of the edge of the deployment doorand the edge of the instrument panel defining the deployment opening.The vinyl covering layer is preferably preweakened by a grooving orcutting of the inside of the covering layer and the system is designedfor the covering layer to sever along the grooving in a defined patternmatching the deployment door. The mispositioning described tends toshift the maximum stress exerted on the covering layer from thepreweakening pattern.

Another problem associated with excessive deformation of the trim piecedefining the deployment opening is that it may be permanently deformedthereby such as to require replacement in the event of an air bag systemactivation even though the collision triggering the activation did notproduce enough vehicle damage to otherwise destroy the trim structure.Accordingly, the replacement of the air bag after activation will alsorequire replacement of the entire instrument panel, substantiallyincreasing the cost of repair.

Accordingly, it is the object of the present invention to provide aconstruction in which the air bag pressure on the deployment door ordoors rapidly and reliably generates a shear stress on the coveringlayer sufficient to cause complete severing thereof and enable thedeployment door to hinge open as quickly as possible to allow properdeployment of the air bag within the passenger compartment.

It is another object of the present invention to stabilize and reinforcethe trim piece structure such as to avoid the destruction of the trimpiece by activation of the air bag system.

SUMMARY OF THE INVENTION

These and other objects of the present invention which will beappreciated upon a reading of the following specification and claims areachieved by constructing the trim piece structure defining thedeployment opening to be stabilized against the distorting effects ofthe forces exerted by the overlying cover layer such as to preventsubstantial deflection of the opening perimeter particularly at the freesides of the deployment door such as to prevent the appreciable bulgingthereof and the negative effects described above.

The stabilization of the trim piece perimeter defining the perimeter ofthe deployment opening is accomplished according to the describedembodiment by providing a frame extending about the deployment openingand attached to or integral with the trim piece structure.

The frame is also preferably anchored to a rigid vehicle substructuresuch as the fire wall mounting the instrument panel preventing the trimpiece structure adjacent the deployment opening from being appreciablydeflected under the loads exerted by the air bag pressure such as tocause shearing stresses to be instantly developed and exerted on thecovering layer by the pressure exerted by the deployment door attemptingto open as the air bag inflates.

The covering skin layer is then very rapidly and reliably severed by thedeployment door pressure to ensure proper deployment of the air bag.

The frame also prevents damage to the instrument panel which wouldrequire replacement, thus reducing repair costs after a systemactivation.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of the passenger side of aautomotive vehicle having an invisible seam deployment door.

FIG. 2 is a fragmentary sectional view taken through the instrumentpanel and deployment door shown in FIG. 1. The section taken along theline 2--2 in FIG. 1.

FIG. 3 is a transverse sectional and fragmentary view of the instrumentpanel and deployment door taken along the section line 3--3 in FIG. 1.

FIG. 4 is a perspective view of the deployment opening frame andanchoring tabs.

DETAILED DESCRIPTION

In the following detailed description, certain specific terminology willbe employed for the sake of clarity and a particular embodimentdescribed in accordance with the requirement of 35 USC 112, but it is tobe understood that the same is not intended to be limiting and shouldnot be so construed inasmuch as the invention is capable of taking manyforms and variations within the scope of the appended claims.

Referring to FIG. 1 an air bag installation depicted is the passengerside installation of an automotive vehicle. A portion of the body 10 isshown in FIG. 1.

The air bag installation is associated with an interior trim piece herecomprised of the instrument panel 12 facing the passenger compartment 14alongside the vehicle driver. The air bag when deployed through anopening, indicated generally at 16, serves to protect the passenger sideoccupants of the vehicle in the manner well known to those skilled inthe art.

The air bag installation according to the present invention includes adeployment door substrate panel 18 located on or beneath the vinylplastic covering layer 20 overlying the instrument panel 12 andextending over the deployment door substrate panel 18.

A surrounding frame 11 extends about the perimeter of the deploymentopening 16. All of these components are hidden from view by virtue ofthe covering layer 20 smoothly and uninterruptedly overlying theinstrument panel region whereat the air bag is installed.

Referring to FIGS. 2 and 3, the deployment door substrate panel 18,typically of a suitable molded plastic material, for aluminum, isconfigured to be interfit within the deployment opening 16 formed in theinstrument panel substrate 22. The deployment door substrate panel 18 isgenerally rectangular and hinged along one side by means of an integralcurved hinging section 24 affixed to the forward side of the instrumentpanel substrate 22 adjacent the opening 16.

A foam layer 26 covers the instrument panel substrate 22 and thedeployment door substrate panel 18 adhered thereto, the covering layer20 also bonded to the foam layer 26. The foam layer 26 is commonlymolded in place by a manufacturing technique well known to those skilledin the art.

An air bag canister 28 is mounted behind the instrument panel 12 at alocation aligned with the deployment opening 16 in the instrument panelsubstrate 22.

The frame 11 is affixed to the instrument panel substrate 22 to theportions thereof which define the perimeter of the deployment opening16. The frame 11 may be of sheet metal or molded plastic such as tostiffen and stabilize the substrate panel 22 in the regions extendingaround the perimeter of the deployment opening 16.

The frame 11 may be secured by rivets 30 as shown. Alternatively, anintegral construction could be employed.

The frame 11 includes down turned sides and a connecting bottom sectionlocated against the perimeter opening the portions of the instrumentpanel substrate 22 extending about the perimeter of the deploymentopening 16.

The downwardly extending flanges 32 and 34 provide a stiffening of theframe 11 against outward bending forces.

The frame 11 and the region adjacent the free side of the deploymentdoor substrate panel 18 opposite the integral hinge 24 is formed with abend defining a supporting stop 36 on which the free side of thedeployment door substrate panel 18 rests such as to be able to resistinward pushing pressure.

An up turned rim of the deployment door 38 creates an edge increasingthe pressure of the deployment door in cutting through the coveringlayer 20.

The covering layer 20 may also be partially scored from the inside asdescribed in U. S. Pat. No. 5,082,310 referred to above.

The free sides of the deployment door panel 18 shown in FIG. 3 rest atopoffset portions of the instrument panel substrate 40.

According to the concept of the present invention, the frame 11 isfurther stabilized by means of a series of anchoring flanges 46A-46C.Flange 46A is secured to the lefthand side of the frame 11, while flange46B is attached to the righthand side and a series of smaller generallytriangular anchoring tabs 46C attached along the front, and rear sidesof the flange 11.

The anchoring tabs 46A-46C are attached to a rigid substructure of thevehicle 48 such as the fire wall to which the instrument panel issecured such as to provide a substantially rigid anchoring feature,preventing appreciable bulging of the instrument panel.

Accordingly, the movement of the deployment opening perimeter portionsof the instrument panel substrate 22 is stabilized and restrainedagainst outward pressures causing a tendency to outwardly bulge anddeform along the three free sides of the deployment door. A shear stressis developed in the covering layer along the deployment door perimeteras rapidly as possible and severing of the covering layer occurs at theearliest possible moment in the deployment cycle. Inturn, this ensuresthat the air bag will deploy properly and rapidly enough to protect thevehicle occupant.

The stabilizing of the instrument panel substrate has the most effect ifaccomplished primarily along the three free sides of the deployment doorsubstrate panel 18.

The air bag installation according to the present invention includes aprocess of forming the deployment opening 16 in the instrument panelsubstrate 22 wherein the opening is aligned with the stored air bag. Thedeployment door substrate panel 18 is fit into the opening and hingedalong one side. The instrument panel substrate 22 is covered with thecovering layer 20 and the frame 11 is fixed to the perimeter of thedeployment opening 16 and the frame is anchored to the rigidsubstructure of the vehicle.

In double door situations, as shown in U.S. Pat. No. 5,082,310, therestraint and stabilization of the instrument panel substrate portionsadjacent the sides of the door will produce this same effect.

The severing of the double door adjoining seam is accomplished by asomewhat different dynamic than the single door deployment doordescribed above.

The restraint of the perimeter of the opening particularly on the freesides of the door should be as great as possible, i.e., the deformationof the perimeter defining portions of the instrument panel substrate ispreferably minimal.

This can be accomplished by the step of anchoring the frame 11 to afixed structure as by means of the anchoring tabs 46 described. Somedeflection can be tolerated but a deflection of no more than 25 mm ofthe substrate adjacent the free side of the deployment door should bethe design criteria.

The anchoring tabs could be dispensed with if a sufficient reinforcingof the instrument panel such as to prevent deflection of the perimeterportions in excess of this distance were thus achieved. However, theincreased weight of the instrument panel likely necessary makes the useof anchoring tabs preferable.

We claim:
 1. An air bag installation for the passenger compartment of avehicle comprising:an interior trim piece mounted in said passengercompartment and having a substrate panel formed with an opening, saidinterior trim piece mounted to a fixed structure in said passengercompartment; an air bag storing canister mounted behind said trim piecesubstrate panel aligned with said opening therein, said air bag storingcanister containing an air bag to be deployed by inflation thereof; atleast one deployment door substrate panel fit into said opening andhinged along one side to a portion of said trim piece substrate paneladjacent said opening; a covering layer extending uninterruptedly oversaid trim piece substrate panel and said deployment door substrate panelto conceal said deployment door substrate panel from view, saiddeployment door substrate panel forced through said covering layer whensaid air bag is deployed; a perimeter stiffening frame extending aroundsaid opening and fixed relative said trim piece substrate panel;anchoring elements attached to said perimeter stiffening frame and tosaid fixed structure in said passenger compartment to thereby stabilizeand restrain the perimeter of said opening from outward bulging uponforcing of said deployment door substrate panel to hinge open byinflation of said air bag and penetrating said covering layer.
 2. Theinstallation according to claim 1 wherein said covering layer is ofvinyl plastic.
 3. The installation according to claim 2 furtherincluding a foam layer interposed between said trim piece substratepanel and said deployment door substrate panel and said vinyl plasticcovering layer.
 4. The installation according to claim 1 wherein saiddeployment door substrate panel is generally rectangular having threefree sides and a hinging side.
 5. The installation according to claim 4further including fixed stops on which said three sides of saiddeployment door substrate panel rests to prevent inward movement.
 6. Amethod of forming an air bag deployment opening in a trim piece in apassenger compartment of a vehicle behind which an air bag is stored forinflation upon activation, said trim piece including a substrate panel,said method comprising the steps of:forming an opening in said trimpiece substrate panel aligned with said stored air bag; fitting at leastone deployment door substrate panel into said opening by hinging said atleast one deployment door substrate panel along one side thereof so asto be able to open by swinging away when pushed by inflation of said airbag; covering said trim piece substrate panel with a covering layerextending uninterruptedly over said trim piece substrate panel and oversaid deployment door substrate panel; anchoring portions of said trimpiece substrate panel defining the perimeter of said opening therein toa stiffening frame and anchoring said stiffening frame to fixedstructure in said passenger compartment so as to limit deflection ofsaid portions to 25 mm or less when said air bag is inflated and saiddeployment door substrate panel is forced to swing open and penetratethrough said covering layer.